The present invention relates to thin-walled bearing bushings produced by a drawing process particularly suitable for the support pins in universal joints. Typically, these bushings comprise an elongated generally cylindrical sleeve section and a bottom section or wall at one axial end of the sleeve section so that the outer peripheral surface of the sleeve section and the exterior face of the bottom section are joined at a peripheral edge which is of a comparatively small cross sectional radius. The bushing includes a continuous groove located radially inwardly and extending axially into either the exterior or the interior surface of the bottom section in the vicinity of the peripheral edge.
A thin-walled bearing bushing manufactured by a deep drawing process is shown in pending application Ser. No. 218,520 filed Dec. 22, 1980, U.S. Pat. No. 4,377,313 which is owned by the assignee of the present application. The bearing bushing shown in this application has a groove which is radially limited toward the inside and located in the bottom section of the bearing bushing in the vicinity of the relatively sharp peripheral edge formed between the surface area of the sleeve and the exterior surface of the bottom section. While the prior bearing bushing is generally satisfactory, it has been found that relatively large shaping and pressing forces must be applied when the groove is formed which produces stresses affecting the material of the bearing bushing unevenly along the periphery particularly in the case of large diameter bearing bushings. Consequently, warpage may occur in the bearing bushing sidewall during the deep drawing of the thin-walled sleeve section of the bearing bushing. As a result, the precision or accuracy of the configuration of the bearing bushing manufactured by a deep drawing process may not always be satisfactory, particularly in the case of large bearing bushings.
With the above in mind, it is an object of the present invention to improve bearing bushings of this type so that they possess a high degree of precision in configuration even in large diameter sizes. It is also an object to provide a means for manufacturing the bearing bushings economically utilizing relatively low molding or drawing forces. To this end, in accordance with the present invention, several grooves of arcuate configuration and separated from one another are provided in the outer or interior face of the bottom section adjacent the edge defining the juncture between the sleeve section and the bottom section. The advantage of this construction is that the grooves in the bottom section can be formed with relatively small shaping and pressing forces of the extrusion die in the matrix. In this manner, a peripheral edge with a requisite small cross sectional radius is formed at least in the area of the grooves. Furthermore, by using discrete grooves in the bottom section, there is a limited material flow towards the periphery during impression of the grooves into the exterior or interior surface of the bottom section. Further, by spacing the grooves, areas with a full wall thickness bridge the grooves. These bridge areas contribute advantageously to the rigidity of the bearing bushing so that the bearing bushing will retain its predetermined shape after being removed from the drawing matrix during transportation and installation in universal joints. The problem of detrimental oval deformation due to residual stress in the groove area which may occur particularly in the case of bearing bushings with large diameters is eliminated.
The grooves are preferably of a V-shaped cross section which widen outwardly in the peripheral direction by reason of the oppositely slanted surfaces at the terminal ends thereof. The purpose of this arrangement is to facilitate material flow in a peripheral direction and thereby during impression of the grooves obtain sections with a true shape between adjacent grooves in the bottom section of the bearing bushing.
The grooves also widen outwardly in a radial direction thereby facilitating flow of material during formation of the grooves and mold a peripheral edge with relatively small cross sectional radius.
In accordance with another feature of the present invention, the grooves at the periphery of the bottom section are formed alternately in the interior and the exterior surface of the bottom section. By doing it in this fashion, the formation of the grooves requires minimal axial force of the drawing ram and the counter ram since for both dies there is only a small number of relatively small grooves to be pressed into the bottom section of the bearing bushing.